Ernst Crows, (6 March 1882-31 May 1967) was a descendant of an old Krefeld Mennonite family. Following his doctoral studies in German history, literature, law, and philosophy, Crous worked in the Prussian state library (Preußische Staatsbibliothek) in Berlin and served as lecturer at the Berlin library school. As head of the incunabula section (books printed before 1501) of the library, as well as through his own research, he soon became known internationally as an authority in this field. In 1925 he was elected to the church council of the Berlin Mennonite congregation, and five years later became its chairperson. He was instrumental in gathering the scattered Mennonites of Berlin into a unified congregation. During the era of National Socialism (Nazism), he and his wife Rose developed a relationship to the Confessing Church. In 1944 the Berlin Library School was transferred to Göttingen, where he also settled.

It was in the Göttingen area that many refugees from West Prussia and Russia found shelter after World War II. Crous played a significant role in providing the refugees in lower Saxony, Westfalia, and North Hesse with spiritual and material help. He became elder of the Mennonite congregation in Göttingen. Soon after World War II he succeeded in convening a conference of Mennonite representatives from Holland, Canada, and North and South Germany in Göttingen to rebuild bridges of understanding which had been destroyed by the war. From 1932 to 1951 Crous served as vice president of the Vereinigung der Deutschen Mennonitengemeinden (Association of [North] German Mennonite Churches), in which capacity he represented German churches in the founding of the World Council of Churches in Amsterdam in 1948. Crous was also instrumental in helping organize in 1947 the Mennonite distribution network for relief assistance coming from North America to the British zone in northern Germany.

He was one of the founders of the Mennonitischer Geschichtsverein (German Mennonite Historical Society) in 1933. From 1947 to 1958 he was editor of the Mennonitisches<em>Lexikon</em>. He collaborated in the preparation of the four-volume MennoniteEncyclopedia, and the third edition of a standard German theological encyclopedia, Die Religion in Geschichte und Gegenwart. He also became chairman of the Täuferaktenkommission (Commission for the Publication of Anabaptist Documents). Research in Anabaptist and Mennonite history remained his preferred academic interest throughout his life. In this connection he wrote more than 380 articles for the Mennonitisches Lexikon and the Mennonite Encyclopedia. Many articles in a variety of other publications further confirm this interest.